This invention relates to an engine system including an internal combustion engine and an exhaust gas recirculation (EGR) system.
It is recognized that, in the conventional engine, a portion of exhaust gas tends to remain in each cylinder when the exhaust stroke has terminated and the amount of such residual gas will increase under partial load conditions, causing unstable engine operation under these conditions. Thus, if the residual gas is expelled from the cylinder and replaced with the same amount of scavenging air, the admission of more fuel to the cylinder is possible because more fuel can be burned with the help of the scavenging air, thus permitting the engine power output to increase when power is demanded. Fuel consumption can be reduced under partial load conditions if the residual gas is replaced with the same amount of scavenging air because the probability of misfiring under these conditions is decreased significantly.